The impact of delayed commencement of adjuvant chemotherapy (eight or more weeks) on survival in stage II and III colon cancer: a national population-based cohort study

BACKGROUND: To examine the impact of chemotherapy delay on survival in patients with stage II or III colon cancer and the factors associated with the delay (≥8 weeks) of adjuvant chemotherapy. METHODS: Patients undergoing curative resection and adjuvant chemotherapy in a national population-based cohort were included. RESULTS: Among 5355 patients, 154 (2.9%) received chemotherapy more than 8 weeks after surgery. Based on a multivariate analysis, the risk factors associated with chemotherapy delay ≥8 weeks were older age [65 to 74 years (hazard ratio [HR]=1.48) and ≥75 years (HR=1.69), p=0.0354], medical aid status in the health security system (HR=1.76, p=0.0345), and emergency surgery (HR=2.43, p=0.0002). Using an 8-week cutoff, the 3-year overall survival rate was 89.62% and 80.98% in the <8 weeks and ≥8 weeks groups, respectively (p=0.008). Independent prognostic factors for inferior overall survival included chemotherapy delay ≥8 weeks (HR=1.49, p=0.0365), older age [65 to 74 years (HR=1.94) and ≥75 years (HR=3.41), p<0.0001], TNM stage III (HR=2.46, p<0.0001), emergency surgery (HR=1.89, p<0.0001), American Society of Anesthesiologists score of 3 or higher (HR=1.50, p<0.0001), and higher transfusion amounts (HR=1.09, p=0.0392). CONCLUSIONS: This study shows that delayed commencement of adjuvant chemotherapy, defined as ≥ 8 weeks, is associated with inferior overall survival in colon cancer patients with stage II or III disease. The delay to initiation of adjuvant chemotherapy is influenced by several multidimensional factors, including patient factors (older age), insurance status (medical aid), and treatment-related factors (emergency surgery).